Are The Project Triple Constraints Still Relevant?

There are many articles recently about the traditional project triple constraints: scope, schedule and budget, and how PMI recently in the PMBOK Guide, Fourth Edition (hereafter, the PMBOK Guide) replaced the triple constraints by a larger list of project constraints that project managers should consider.

The list of project constraints proposed by PMI is an extension of the triple constraints. Besides scope, schedule and budget, it includes resources, quality and risks. And it is not the full list, to quote the PMBOK Guide:

Managing a project typically includes:

• Identify requirements,
• Addressing the various needs, concerns, and expectations of the stakeholders as the project is planned and carried out,
• Balancing the competing project constraints including, but not limited to:

1. Scope,
2. Quality,
3. Schedule,
4. Budget,
5. Resources, and
6. Risk.

So, are the traditional project triple constraints still relevant? Here are some of my thoughts

The triple constraints remain one of the most important tools for project managers to analyze projects and communicate project objectives and constraints with stakeholders.

To effectively analyze and communicate about projects, project managers need a simple, yet sufficient, tool. There are, certainly, many competing project constraints. But they are all in some way can be converted to scope, budget, or schedule. Therefore, the main purpose of using this tool is not to cover as many constraints as possible, but to emphasize the most relevant and important constraints.

The PMI’s list of project constraints help project teams analyze their projects from different viewpoints

Compactness is not always good. If there is time available, in many cases it is useful to analyze project from different viewpoints. That is where the PMI’s list of project constraints can be used.

• A change request can have many impacts: an addition to project scope, a new quality requirement, a requirement for more resources. A change request can raise new risks, too. Therefore, a project manager should review a full list of project constraints in order to ensure that she has taken all aspects into consideration.
• The relationship of scope, quality and schedule is not a linear one, as Glen B. Alleman mentioned in his article. Project management software, like Microsoft Project, consider this relationship a linear one: you defined resources productivity, resources for each task, and then by changing the resources available for a task you can see a proportional change in the time needed to accomplish it. However, it is not so simple in real life. Doubling resources for a task does not surely accelerate the accomplishment by two times. Adding resources to a task may add more risks, communication requirements between resources and so may even take people longer to finish their job! Therefore, it is very important that a project manager considers relationship between project constraints more thoroughly.